The Challenge:

Kier and BAM Nuttall, with their specialist geotechnical division BAM Ritchies, are in a fully integrated joint venture to deliver the OH2001 Earthworks, site preparation and infrastructure for the new nuclear power station at Hinkley Point C (HPC).

The power station will incorporate two 1650 Megawatt European Pressurised nuclear reactors (EPR), together capable of generating electricity for approximately 5 million homes and a range of shared facilities and is set to generate around 6% of the UK’s electricity, all of which will be low carbon. Situated over a site 2.1km x 2.2km wide (the equivalent to 245 football pitches!) adjacent to the Severn Estuary, HPC is approximately five miles from Bridgwater and the M5. At the peak of construction, it is anticipated the Kier BAM Joint Venture will have a workforce of c1,500 people.

The Solution:

Works included:

  • Three million tonnes of concrete used to construct the power station.
  • Excavation of areas including the main reactor dig, and the processing and placement of engineered and landscaped fills. Excavation of approximately 5.6million m³ of rock and overburden and the treatment and reuse of the material.
  • Site preparation and restoration – remediation, stockpile management and restoration.
  • Roads and networks approximately 15km of construction phase roads, a north bus and south delivery plaza, ducts, drainage (40,000m) a water main and street lighting.
  • Structures, including a 760-metre-long sea wall, a 400-metre piled wall, multiple retaining walls and temporary and permanent bridges.

Much of the excavated material will be transferred to the adjacent Holford Valley.

The Impact:

A deep dig area which involves the construction of the foundations for the nuclear power station. The deep dig entails deep excavation which will sink to approximately 31 metres at the deepest level. Soil nailing (c100,000m) and spray concreting (38,000m³) operations will be undertaken during the construction of the excavation faces. Placement of rock protection blinding concrete (foundations to the nuclear structure) using nuclear grade concrete delivered to nuclear quality standards.

To protect the Holford stream we built a 700m long culvert, allowing the stream to keep flowing through a concrete box. The culvert comprises 597 precast concrete sections, each measuring 3.2m wide by 3.35m high. Quality was incredibly important, and inspections of the precast concrete sections were completed before they were put in place.

Installation of earthing system under nuclear buildings to nuclear standards. Facilitating the deep dig / excavation works will be the installation and operation of a de-watering system which comprises multiple pumped de-watering wells. At peak, the deep dig section will be placing around 2,000m³ per week.

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